Strange messages after migrating from 5.x to 6.0.13 on Ubuntu

After Migration on Ubuntu 6.04 from zimbra 5.0.x to 6.0.13 Network Edition in zmmailboxd.out appaer every socond lots of this messages:

Code:

Total time for which application threads were stopped: 0.0000820 seconds
Total time for which application threads were stopped: 0.0000800 seconds
Total time for which application threads were stopped: 0.0001140 seconds
Total time for which application threads were stopped: 0.0000770 seconds
Total time for which application threads were stopped: 0.0001210 seconds
Total time for which application threads were stopped: 0.0003040 seconds